Reuben Saltzman: How to prevent an Ice Dam

We’ve received over 34″ of snow in Minnesota in the last 25 days, which makes this the snowiest December on record.  While the snow turns our state in to a beautiful white winter wonderland, it also causes nasty ice dams that wreak havoc on homes like never before.

Icicles

The heavy amount of snowfall and temperatures in the teens have been the perfect conditions to create ice dams.  Water leakage from ice dams is an epidemic in Minnesota right now.  I have friends, neighbors, and family members with water leaking in to their homes.  It’s everywhere.  I’ve taken all of the photos below within the last two weeks.

Water in wall

Ice Dam

Ice on wall

Wet Insulation

Damaged Ceiling

Water at ceiling

The two things that everyone wants to know is how to get rid of ice dams and how to prevent ice dams.  As I mentioned in a previous blog, the only completely safe and effective way to get rid of ice dams is to hire a professional ice dam removal company; they’ll use steam, which will completely remove the ice dam.  Anything else is a hack method.

The best way to prevent ice dams from forming is to address the three factors in your attic that contribute to ice dams; insulation, ventilation, and attic bypasses.

Attic Bypasses (air leakage)

This is the largest contributor to ice dams.  In almost every house that I inspect to determine the cause of ice dams, I find attic bypasses directly below the beginnings of the ice dams.  Attic bypasses are passageways for warmed air to enter in to the attic space, and traditional insulation won’t fix this.  The photos below show some common attic bypasses that I can find in just about any older house.

This first photo shows one of the largest and most common bypasses – the space around the furnace and / or water heater vent.  Sometimes these are huge. The one shown below is quite small.

Bypass at furnace vent

In the photo below, you can see several holes in the top plate of a wall that were drilled for wires to pass through.  These holes could all be easily filled with spray foam, but finding these holes all over the attic would be a challenge without first removing the insulation.

Bypasses at bore holes

With additions, the transitions between the ‘new’ and ‘old’ construction seem to always be sources of attic bypasses.  I had to dig through a lot of insulation to find this gap, but I wasn’t surprised at what I found.

Bypass at addition

When plumbing vents enter in to the attic, the space around the vents needs to be sealed.  This one obviously wasn’t.

Bypass at plumbing vent

Some older houses have whole-house fans that are designed to run on hot summer nights; these fans are gigantic sources of heat loss, because they’re usually not insulated or sealed up.  I took the photo below from inside the attic without a flash on my camera.  There’s some crazy heat loss occurring there, and as you might imagine, there was a huge ice dam nearby.

Bypass at attic fan
What makes most of these attic bypasses so difficult to locate is that they’re almost always buried in insulation.  Finding these buried air leaks turns in to an educated guessing game.  Lately I’ve been using an infrared camera while doing ice dam inspections, and I’ve found it to be very useful for finding these hidden passageways.

If you plan to have more insulation added to your attic, it’s probably a worthwhile investment to have all of the existing insulation completely removed and the bypasses sealed up before you re-insulate.  There’s just no way to find all the bypasses if you don’t do this.  If your home is over 20 years old, it’s almost a guarantee that you’ll have attic bypasses that need to be sealed.  It’s a shame that so many insulation contractors just add insulation on top of what’s already there without sealing the bypasses.

I also practice what I preach; I’m such a firm believer in removing insulation and sealing bypasses before re-insulating that I did this at my own house, my parents had this done at their house, and my sister had this done at her house.  It makes a big difference.

Insulation

This is a basic concept that everyone understands; you need insulation in your attic.  If there are voids in the insulation, they need to be fixed.

My first choice would be to have about two inches of closed-cell foam insulation applied to the attic floor, and then have several inches of cellulose installed on top of that.  The closed cell foam would seal up every bypass, and the cellulose would be a cost effective way to get the insulation level up to current requirements.  The drawback with this method is cost; closed cell foam ain’t cheap.

My next choice of insulation would be all cellulose insulation, with all of the bypasses sealed first.  I prefer cellulose to loose-fill fiberglass because it has a higher insulating value per inch, it seems to do a better job of stopping air leakage, and it’s not itchy fiberglass.  I’ve been digging through a lot of fiberglass covered attics lately, and my arms start getting itchy just thinking about it.

My last choice of insulation would be loose-fill fiberglass insulation… not that there’s anything wrong with it.  I personally just don’t like dealing with fiberglass.

What about fiberglass batts?  You know, those big rolls of fiberglass?  No way, Jose.  That stuff is impossible to install properly.  Fiberglass batts leave gaps all over the place that add up to an exponential level of heat loss.  I’m pretty sure that fiberglass batts are installed in attics exclusively by handy homeowners.

Ventilation

Having adequate ventilation for the attic space will help to keep the roof surface cold, which will help to prevent snow from melting, which will help to prevent ice dams.  The best way to ventilate an attic space is with continuous soffit vents and continuous ridge vents, but this isn’t always possible.

If you don’t have enough soffit vents, add more.  If you don’t have enough roof vents, add more.  You can’t have too much ventilation.  If your soffit vents are dirty, clean ‘em or replace the grills if they’re painted shut.  Grills are cheap.  If your soffit vents are blocked with insulation, you need air chutes installed at the eaves to prevent the insulation from blocking the vents.

Reuben inspecting ice damsWhen all else fails…

If you’ve already done everything you can think of to fix your ice dams but they keep coming back, or you’ve hired a contractor to fix your ice dams but they seem to be scratching their head a lot or coming up with a bunch of different guesses, call a home inspector.  We look at this stuff every day, and some of us even specialize in ice dam inspections.

In some cases, it’s not cost effective to control ice dams from inside.  Next week I’ll be blogging about controlling ice dams from the exterior.

This post was written by Reuben Saltzman and originally published on Reuben’s Structure Tech Home Inspection Blog.

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Comments (8)

  1. Submitted by Laura Gilbert on 12/29/2010 - 09:53 am.

    Wow! That is some of the best and most helpful advice I’ve read about ice dams. Please consider writing another blog down the road on how to assess if the ice dam did roof damage! thanks.

  2. Submitted by Reuben Saltzman on 12/30/2010 - 05:22 am.

    Thanks Laura, I’ll definitely consider that. I’m always looking for new topics to write about.

  3. Submitted by Paul Udstrand on 12/30/2010 - 09:24 am.

    Snow, ice, and icicles are nothing new. Roofs are designed to keep water out of houses. I’m tired of these yearly sales pitches pretending to be helpful advice. Do you have ice dams? Well you better spend hundreds or thousands of dollars to get it fixed!

    Just because you have an ice damn doesn’t mean you have a problem. It doesn’t mean you have water infiltrating you’re walls. And you will have ice damns pretty much every year, this is not a new phenomena created by a snowy winter or weird temperatures.

    Every year now we get these alarming “news” stories about ice dams and how we all have to hire professionals to remove them. These “stories” are as predictable as holiday shopping stories. Doesn’t anyone ever bother to ask where these professionals have been for the last two thousand years? Did anyone steam ice dams off your house 20, 30, 40, or 50 years ago? Did we all grow up with water pouring into our living rooms every winter and rotting walls?

    Roofing materials are better now than they’ve ever been. Self sealing ice barriers that extend 24 inches beyond the inside wall are required by code in MN. That means in most cases you have about six feet of ice barrier extending up from the edge of your roof. Why is this code? Because ice dams are nothing new and roofs are designed to cope with them.

    If you have water damage it’s because your roofing failed, not because you have an ice dam per-se. Most roofs in MN can cope with ice dams. Mr. Saltzman has a lot of photos but remember what he does for a living. You’d have a lot of photos to if your job was to investigate complaints of water damage.

    I’m not saying that ice dams can’t be a problem. In fact my folks just had water pour into their kitchen because of an ice damn. However roof design had more to do with that than the existence of ice dams. They have no overhang and the roof flattens out in that area. I grew up in that house, there are ice dams every year, obviously the ice barrier finally failed.

    Good insulation is always a good idea, as is sealing holes and good ventilation. But just because you see an ice dam or big icicles up there doesn’t mean you have a problem, and dams to some degree are inevitable on any roof regardless of insulation. It would be nice if someone would talk about how to tell if you actually have a problem instead of simply pointing to an ice dam and telling you to hire a professional to steam if off. The question is weather or not your ice dam is a problem, not simply weather or not you have an ice dam. My house if 50 years old, I have ice dams and big icicles every year. I just took part of the soffit down when we replaced a bay window; no hint of water damage whatsoever.

    Obviously there are those who would love it if everyone in MN hired someone to remove ice dams every winter but it’s simply not necessary. By the way, you do all realize that an ice dam removed will just form again once snow piles up on the roof again right? In a snowy winter your looking at doing that two or three times.

  4. Submitted by Jeff Mogush on 12/30/2010 - 01:44 pm.

    I agree with Laura. You communicated extremely well by use of prose and photos.

    I have ice dams on my unheated garage. I looked into the eave, from inside the garage, and could see light entering from the vents. The temperature is above freezing and the vents are dripping with water. Am I concluding correctly that I should install a wall on the garage side of the vents, seal the edges of the wall, and then insulate between the new wall and the garage?

  5. Submitted by Gregory Lang on 12/30/2010 - 02:21 pm.

    Good advice! When I bought my Sears catalog bungalow house in 1986 it had air-gap wiring and only a couple of inches or “rock-wool” insulation in the attic. The ceiling lights were literally holes into the attic. I installed steel electrical boxes and steel encased wiring in the attic. Then I used wet plaster to seal up the air gaps around all the light fixtures. I used canned foam to seal up all other air gaps into the attic. With little insulation they were easy to find. After that I added massive quantities of roll fiberglass unfaced insulation. I would guess it is now an average of two feet deep.

    My 25 year old two-layer roof seems to be holding up very well. I’ve been told it might go another five to ten years. Only a little ice on the bungalow overhang, no evidence of moisture getting into the house.

    The neighbors tell me that my house used to be the worst on the block for ice dams.

    It took a couple of days for the roof vents to “breath”. A taller redesign might be advisable on these.

    That said, you think of ice dams when water starts leaking in. Not a drop at my http://SearsHouse.com

    Older houses can be made very resilient and energy efficient. I signed up for the “house doctor” air infiltration thing after the attic project. I did most of the work myself. In summer my bungalow is cool enough so that I don’t need central air (just two 10 watt fans exhausting out of the piano windows). Before the insulation heat would radiate from the attic in the summer. In winter the house is “tight” so no draftiness and very low heating bills. This is a 90 year old house.

  6. Submitted by Reuben Saltzman on 04/21/2011 - 05:33 am.

    Hi Mr. Udstrand,
    I wish I had noticed your comment sooner. You had a lot to say, and most of it was misleading or just plain wrong. I’ll try to address your statements individually.
    “I’m tired of these yearly sales pitches pretending to be helpful advice.” ***** That’s just downright offensive. I’m explaining what causes ice dams, and I’m explaining how to fix them. I don’t do the repairs myself, so what could I be selling?
    “It doesn’t mean you have water infiltrating you’re walls. And you will have ice damns pretty much every year, this is not a new phenomena created by a snowy winter or weird temperatures.” ***** That’s wrong. Most newer houses don’t have “ice damns” [sic].
    “Every year now we get these alarming “news” stories about ice dams and how we all have to hire professionals to remove them. These “stories” are as predictable as holiday shopping stories. Doesn’t anyone ever bother to ask where these professionals have been for the last two thousand years?” ***** Two thousand years? Are you kidding?
    “Did anyone steam ice dams off your house 20, 30, 40, or 50 years ago?” ***** No, they didn’t have steamers. People did get up on roofs and shovel the snow off, and people did use all kinds of hack methods to get rid of ice dams. When my dad was a teenager, he made extra money in the winter by shoveling snow off his neighbor’s roofs and using a tree saw to cut draining channels in ice dams.
    “Did we all grow up with water pouring into our living rooms every winter and rotting walls?” ***** It didn’t happen every winter, and it doesn’t happen every winter. It did happen though. These last two years have been especially problematic.
    “Roofing materials are better now than they’ve ever been.” ***** What are you basing that on?
    “Self sealing ice barriers that extend 24 inches beyond the inside wall are required by code in MN. That means in most cases you have about six feet of ice barrier extending up from the edge of your roof. Why is this code? Because ice dams are nothing new and roofs are designed to cope with them.” ***** That wrong. Roofs are designed to resist leakage from small ice dams. Eave protection is definitely not a guarantee against leakage from ice dams.
    “If you have water damage it’s because your roofing failed, not because you have an ice dam per-se.” ***** That’s wrong. Sloped roofs are designed to shed water; they’re not waterproof. When water is backed up more than 24″ beyond the inside wall, it’s going to leak in to the house.
    “Most roofs in MN can cope with ice dams.” ***** That’s wrong. Most roofs can cope with ‘average’ ice dams. When the ice dams are much bigger than usual, most roofs can’t.
    “Mr. Saltzman has a lot of photos but remember what he does for a living. You’d have a lot of photos to if your job was to investigate complaints of water damage.” ***** My job is to inspect houses, and most of my clients are home buyers. I investigate these water complaints on the side.
    “Good insulation is always a good idea, as is sealing holes and good ventilation. But just because you see an ice dam or big icicles up there doesn’t mean you have a problem, and dams to some degree are inevitable on any roof regardless of insulation.” ***** Again, that’s just plain wrong. Most newer houses don’t have ice dams.
    “It would be nice if someone would talk about how to tell if you actually have a problem instead of simply pointing to an ice dam and telling you to hire a professional to steam if off.” ***** Who is pointing to an ice dam and telling you to hire a professional to steam it off?
    “The question is weather or not your ice dam is a problem, not simply weather or not you have an ice dam.” ***** Easy. It’s not a serious problem until water leaks in to the house. If you have major ice dams, you have major heat loss. This is usually something that can be corrected.
    “My house if 50 years old, I have ice dams and big icicles every year. I just took part of the soffit down when we replaced a bay window; no hint of water damage whatsoever.” ***** That’s anecdotal evidence.
    “By the way, you do all realize that an ice dam removed will just form again once snow piles up on the roof again right?” ***** You’re insulting the intelligence of anyone reading your comments with a statement like that.
    “In a snowy winter your looking at doing that two or three times.” ***** Perhaps what you do not understand that the people who hire a professional to remove their ice dams are doing it because they have water pouring in to their house, or they’ve already had water pouring in to their houses and they don’t want it to happen again. The entire purpose of this blog is to tell people what they can do to prevent this from happening, so they don’t have to hire someone to come steam their ice dams.
    This isn’t a sales pitch, Mr. Udstrand.

  7. Submitted by Reuben Saltzman on 04/22/2011 - 04:57 am.

    Jeff M – you wrote “Am I concluding correctly that I should install a wall on the garage side of the vents, seal the edges of the wall, and then insulate between the new wall and the garage?”

    Probably not, but I’m having a hard time picturing your house. Is this a rambler? When was it built?

  8. Submitted by Reuben Saltzman on 04/22/2011 - 04:59 am.

    Greg – it sounds like you did a great job of insulating your attic. It’s amazing how well the insulation can keep out the heat as well as the cold, isn’t it?

    – Reuben

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